1. Field of the Invention
This invention relates to a speaker assembly for a motor vehicle. More particularly, the invention relates to an automotive speaker assembly in which the speaker is mounted to a blow molded enclosure so as to minimize vibration of the enclosure. The invention also relates to an automotive speaker assembly having a speaker wire which extends into the enclosure through the same opening that receives the speaker.
2. Description of Related Art
High performance automotive speakers are typically mounted within plastic speaker enclosures such that sound waves radiating from the front of the speaker diaphragm enter the passenger compartment of the vehicle while sound waves emanating from the back of the speaker diaphragm enter the enclosure. For an automotive speaker to deliver accurate sound reproduction, especially in the low frequency ranges, it is important that the speaker enclosure be rigid enough to resist vibrating in response to the motion of the vehicle and the sound waves generated by the back of the speaker diaphragm. This rigidity requirement represents a significant design challenge in the manufacture of light weight, low cost speaker enclosures. Whereas thin-walled enclosures are desirable from a cost and weight standpoint, care must be taken to ensure that the enclosure walls are adequately reinforced against vibration so that the sound quality of the system is not compromised.
Conventional automotive speaker enclosures are made from injection molded plastic material. The injection molding process allows the thickness of the enclosure walls to be varied such that thicker wall sections may be provided in areas of the enclosure that would otherwise be susceptible to vibration. It is also possible to reinforce injection molded enclosures by providing internal hollow columns, or kiss offs, between the front and rear enclosure walls. Despite the design flexibility offered by injection molding, however, the method has several drawbacks with respect to speaker enclosure manufacture. Tooling and material costs, for example, are relatively high, and additional fabrication and sealing costs are incurred in assembling the enclosure from separately molded pieces. Moreover, it is difficult to ensure an airtight seal between the enclosure pieces because of part shrinkage and the irregular shape of most speaker enclosure designs. In the absence of an airtight seal between the pieces, the speaker enclosure will not function as intended.
Each of the above drawbacks may be overcome through the use of blow molded speaker enclosures. Blow molding tooling and equipment is generally much less expensive than injection molding tooling and equipment, and low cost materials, such as polyethylene, may be used. Furthermore, since blow molded enclosures are one-piece integral structures, no post-mold assembly and sealing operation is required, and the potential for air leakage is reduced.
Blow molded enclosures, like injection molded enclosures, are desirably reinforced against vibration. Because it would be difficult to form a blow molded enclosure having internal kiss offs, or walls of closely-controlled varying thickness, however, other methods for reinforcing the blow molded enclosure must be used. U.S. Pat. No. 4,905,860 to Kurihara et al. discloses one such method, wherein U-shaped ribs are provided on flat regions of the front and back surfaces of a vented, blow molded enclosure to improve its rigidity. Such surface ribs may not provide adequate reinforcement against vibration, however, especially for very thin-walled or unvented enclosures. It would therefore be desirable to provide another mechanism for reinforcing the walls of blow molded speaker enclosures.
A need also exists for an improved wiring system for automotive speaker assemblies. In the present system, a conventional round 16 to 18 gauge speaker wire must be threaded through an aperture in one of the enclosure walls to electrically connect the speaker to an amplifier located outside of the enclosure. Where a vented enclosure is used, the wire may be passed through the vent, but where an unvented enclosure is used, a special aperture for the wire must be provided in the enclosure wall. In either case, the need to thread the wire through the enclosure prevents the installation of the speaker and amplifier as a single, preconnected and pretested unit. The threading operation also adds to the complexity of the assembly process and increases the cycle time. For speaker assemblies having unvented enclosures, the time, expense and complexity of the assembly process is further increased by the need to seal the aperture around the speaker wire. Given these difficulties associated with the conventional wiring system, it would be desirable to provide a speaker assembly having simple and economical means for electrically connecting the speaker to the amplifier.